The present invention relates to a device for protecting guide vanes of hydraulic machines such as hydraulic turbine, particularly Francis turbine, Deriaz turbine and propeller type hydraulic turbines, as well as pump turbine of the same type. More particularly, the invention is concerned with a device for protecting the guide vanes of hydraulic machines of the kind mentioned above, against the breakage due to mutual collision of the guide vanes which take places when one or more guide vanes are freed to oscillate freely by the force of water pressure due to breakdown of weakened pins as a result of jamming of foreign matters in the guide vanes.
When a foreign matter is caught between two or more guide vanes or between the end of a guide vane and a stay vane of a hydraulic turbine during the running, the guide vanes are prevented from rotating.
In order to permit the separation of these guide vanes not rotatable from the controlling link mechanism, these vanes are connected to the link mechanism through weakened pins. When an extraordinarily large force is generated in the guide-vane operation mechanism, the weakened pin is broken at its weak point thereby to protect the guide-vane operation mechanism against the breakdown. After the breakage of the weakened pin, the guide vane or vanes separated from the guide-vane operation mechanism are freely rotated by the hydraulic action to vibrate in a flapping or rattling manner.
In order to overcome this flapping vibration of the separated guide vanes, it has been proposed to use a resilient or elastic washer which produces a braking or damping force. This, however, cannot provide an effective braking or damping force.